Resolving Novopay problems has cost schools at least $8 million in unpaid overtime and interest, a New Zealand Principals' Federation survey shows.

Federation president Philip Harding is pushing the Government for financial compensation.

Cabinet minister Steven Joyce, tasked with resolving the payroll system problems, has said he will look at compensation "in due course".

Novopay has caused serious financial problems for schools and individuals since it was launched last August.

More than 1000 of 2242 schools that are members of the federation responded to the latest online survey, which is sent out after each pay period. The survey showed that 1030 schools believe they are collectively owed an estimated $8m.

"Extrapolating that figure to all 2242 schools brings the total to over $16m," Harding said.

That amount did not reflect the "emotional heartache" that staff endured each pay period, not knowing if they would be paid.